1. Field of the Invention
The present invention relates to an ion implantation apparatus, and more specifically to a focused ion beam implantation apparatus comprising means for inclining a focused ion beam at a large angle with accurate positioning.
2. Description of Related Art
Ion implantation is the introduction of energetic, charged particles into a target such as semiconductor wafer, etc. Ion implantation has been mainly used in semiconductor technology to change the electrical properties of the particular region in the semiconductor substrate. In semiconductor technology, it is not necessary to form an ion-implanted region in complicated shape, so that the ion beam is only scanned relative to the target.
Recently, ion implantation has been applied to processing of an oxide superconductor thin film such as Y-Ba-Cu-O type oxide superconductor, Bi-Sr-Ca-Cu-O type oxide superconductor or Tl-Ba-Ca-Cu-O type oxide superconductor. For example, by implanting proper ion into the oxide superconductor thin film, an insulating region is formed in the oxide superconductor thin film so that a specified superconducting region can be left without damaging the oxide superconductor thin film itself. By contrast, superconducting properties of the oxide superconductor are easily spoiled, if the oxide superconductor thin film is processed by a conventional etching process. In addition, fine processing is possible by using a finely focused ion beam. Therefore, ion implantation is considered one of the best means for processing the oxide superconductor thin film.
In order to manufacture a superconducting device using the oxide superconductor, it is necessary to form an insulating region having a complicated sectional shape in the oxide superconductor thin film. Thus, it is necessary to implant an ion beam at various incident angles with accurate positioning.
However, as mentioned above, a conventional ion implantation apparatus used in semiconductor technology is not designed to incline the ion beam at a large angle relative to the target. If the target is inclined so as to implant the ion beam at a large incident angle, the position at which the ion beam is implanted may deviate. As a result, it has been difficult to form the insulating region having a complicated sectional shape in an oxide superconductor thin film with precise positioning. For example, even if the ion beam is focused to narrower than 0.1 .mu.m, the positioning of the ion-implanted region has to be determined with accuracy better than 0.02 .mu.m.